Centrifugal fan and impeller thereof

ABSTRACT

A centrifugal fan includes a fan frame ( 20 ) and a fan impeller ( 10 ) received in the fan frame. The fan impeller includes a hub ( 12 ) and a plurality of fan blades ( 14 ) extending radially from an outer periphery of the hub. Each of the fan blades has a leeward lateral surface ( 144   a ) and an opposite windward lateral surface ( 144   b ) as the fan impeller rotates. At least one of the fan blades has a rib ( 146 ) protruding longitudinally and outwardly from the leeward lateral surface of the fan blade. The rib is located adjacent to an outmost free end of the fan blade and adapted for blocking an airflow generated by the fan impeller to flow back towards the fan blades of the fan impeller.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to an impeller, and more particularly to a centrifugal fan incorporating the impeller having low noise.

2. Description of Related Art

With continuing development of the electronic technology, electronic packages such as CPUs are generating more and more heat which is required to be dissipated immediately. Cooling fans are commonly used in combination with heat sinks for cooling the CPUs and other electronic products.

Since most of electronic systems that contain electronic components therein such as laptop computers, or notebook computers do not have enough space therein, a centrifugal fan which requires only a small space for installation is generally used. The centrifugal fan typically includes a stator and a rotor being rotatable with respect to the stator. The rotor includes an impeller and a shaft extending downwardly from the impeller. The stator includes a bearing in which the shaft is ratatably received. In use, the impeller of the centrifugal fan rotates to engender an airflow towards the electronic component to cool the electronic component continuously. In order to improve cooling and heat dissipation efficiency, the most direct and effective way is to increase the revolving speed of the impeller to relatively increase the flow rate of the airflow. However, increasing the revolving speed of the impeller causes a noise level generated by the rotating fan to be also increased, thus making an user near the fan to feel uncomfortable.

What is needed, therefore, is an impeller and a centrifugal fan with the impeller which can overcome the above-mentioned disadvantage.

SUMMARY OF THE INVENTION

The present invention relates, in one aspect, to a fan impeller. According to a preferred embodiment of the present invention, the fan impeller includes a hub and a plurality of fan blades extending radially and outwardly from an outer periphery of the hub. Each of the fan blades has a leeward lateral surface and an opposite windward lateral surface. At least one of the fan blades has a rib protruding longitudinally and outwardly from the leeward lateral surface of the fan blade. The rib is located adjacent to an outmost free end of the fan blade and is adapted for blocking an airflow generated by the fan impeller to flow back towards the fan blades of the fan impeller.

The present invention relates, in another aspect, to a centrifugal fan. According to a preferred embodiment of the present invention, the centrifugal fan includes a fan frame and an impeller rotatably received in the fan frame. The fan frame includes a bottom base, an opposite top cover and a side wall interconnecting the base with the cover. The fan impeller includes a hub and a plurality of fan blades extending radially and outwardly from an outer periphery of the hub. Each of the fan blades has a leeward lateral surface and an opposite windward lateral surface. At least one of the fan blades has a rib protrudes longitudinally and outwardly from the leeward lateral surface of the fan blade. The rib is located adjacent to an outmost free end of the fan blade and is adapted for blocking airflow rebounded by the side wall of the fan frame to flow back towards the fan blades of the fan impeller.

Other advantages and novel features of the present invention will become more apparent from the following detailed description of preferred embodiment when taken in conjunction with the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present centrifugal fan can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present centrifugal fan. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.

FIG. 1 is an isometric, assembled view of a centrifugal fan in accordance with a preferred embodiment of the present invention;

FIG. 2 is an exploded view of the centrifugal fan of FIG. 1;

FIG. 3 is an enlarged view of an impeller of the centrifugal fan of FIG. 1;

FIG. 4 is a cross sectional view of the centrifugal fan of FIG. 1;

FIG. 5 is an enlarged view of an impeller in accordance with a second embodiment of the present invention; and

FIG. 6 is a cross sectional view of a centrifugal fan with the impeller of FIG. 5 being incorporated therein.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1 and FIG. 2, an impeller 10 for a centrifugal fan of a preferred embodiment of the present invention is shown. The impeller 10 is received in a fan frame 20 of the centrifugal fan.

The fan frame 20 includes a top cover 21 arranged at a top side of the impeller 10, a bottom base 22 paralleled to the top cover 21 and arranged at a bottom side of the impeller 10, and a side wall 23 interconnecting the top cover 21 and the bottom base 22 and surrounding the impeller 10. The top cover 21, the bottom base 22 and the side wall 23 cooperatively define an inner space (not labeled) for receiving the impeller 10 therein. A first air inlet 24 a is defined in a central portion of the top cover 21 and a second air inlet 24 b is defined in a central portion of the bottom base 22. An air outlet 25 is defined in one side of the side wall 23 of the fan frame 20 and is oriented perpendicularly to the air inlets 24 a, 24 b.

The impeller 10 is driven by a stator (not shown) of the centrifugal fan to be rotatable with respect to the stator in the fan frame 20. Referring to FIG. 3, the impeller 10 includes a hub 12, a plurality of fan blades 14 extending radially and outwardly from an outer periphery of the hub 12, and a blade ring 16 fixedly mounted on a top surface of each of the fan blades 14 at a position near an outmost free end of each of the fan blades 14. The hub 12 includes a circular top wall 120 and an annular side wall 122 extending downwardly and perpendicularly from a rim of the top wall 120. A cylindrical space (not shown) is defined in the hub 12 by the top wall 120 and the side wall 122 cooperatively for accommodating the stator therein.

The fan blades 14 extend radially and outwardly from the side wall 122 of the hub 12. Each of the fan blades 14 includes a first blade portion 142 fixed to the side wall 122 of the hub 12, a second blade portion 144 bent slantwise and smoothly from a distal end of the first blade portion 142, and a rib 146 formed longitudinally on a lateral surface of the second blade portion 144 adjacent to the outmost free end of each of the fan blades 14. The first blade portion 142 of each of the fan blades 14 is planar-shaped and extends from the side wall 122 of the hub 12 along a clockwise direction, as viewed from FIG. 3, while the second blade portion 144 of each of the fan blades 14 is curved as arc-shaped and extends along an anti-clockwise direction, as viewed from FIG. 3. In the present embodiment, the impeller 10 rotates anticlockwise as the centrifugal fan operates. Thus, the second blade portion 144 has a leeward lateral surface 144 a and a windward lateral surface 144 b at an opposite side of the second blade portion 144, wherein the rib 146 extends outwardly from the leeward lateral surface 144 a of the second blade portion 144. The windward lateral surface 144 b contacts with the airflow when the impeller 10 rotates anti-clockwise. Each of the first blade portions 142 has a top face and an opposite bottom face. The top face of the first blade portion 142 extends upwardly along an extension direction of the first blade portion 142, and the bottom face of the first blade portion 142 extends downwardly along the extension direction of the first blade portion 142, thus a longitudinal height of the first blade portion 142 being gradually increased as the first blade portion 142 extends outwardly from the hub 12 towards the second blade portion 144. Each of the second blade portions 144 also has a top face and an opposite bottom face. The top face and the bottom face of the second blade portion 144 are parallel to the top wall 120 of the hub 12, a longitudinal height of the second blade portion 144 being constant as the second blade portion 144 extends outwardly from the corresponding first blade portion 142.

The rib 146 has a rectangular configuration and extends along a longitudinal direction of the second blade portion 144 from the bottom face to the top face of the second blade portion 144. The rib 146 protrudes outwardly from the leeward lateral surface 144 a of the second blade portion 144. In other words, the rib 146 protrudes outwardly and points towards a direction that is contrary to the rotating direction of the impeller 10. An angle θ formed between the rib 146 and the outmost free end of the fan blade 14 is about 65 degrees, which makes the outmost free end of the fan blade 14 and the rib 146 have a V-shaped configuration.

The blade ring 16 and the fan blades 14 are integrally formed by injection molding process as a single piece. The blade ring 16 includes an annular, planar connecting wall 160 and a sidewall 162 extending perpendicularly and upwardly from an inner periphery of the connecting wall 160. An outer diameter of the connecting wall 160 is approximately the same as an outer diameter of the second blade portions 144 of the fan blades 14, and an inner diameter of the connecting wall 160 is a little smaller than that of the first blade portions 142 of the fan blades 14. Thus, the connecting wall 160 of the blade ring 16 fully covers on the top faces of the second blade portions 144 of the fan blades 14, and an outer periphery of the connecting wall 160 is substantially aligned with an outmost longitudinal edge 145 of each of the fan blades 14. Referring to FIG. 4, the connecting wall 160 of the blade ring 16 and the fan blades 14 are both located just under the top cover 21 of the fan frame 20, the sidewall 162 of the blade ring 16 extends upwardly from the inner periphery of the connecting wall 160 and is received in the first air inlet 24 a of the centrifugal fan. A top surface of the sidewall 162 of the blade ring 16 is located in a same horizontal level with a top surface of the top cover 21. For avoiding contact and friction between the impeller 10 and the fan frame 20 as the impeller 10 rotates relative to the top cover 21 of the centrifugal fan, a radial clearance of about 0.5 mm is formed between the sidewall 162 of the blade ring 16 and the top cover 21, an axial clearance of about 1 mm is formed between the connecting wall 160 of the blade ring 16 and the top cover 21, and an air flow channel 30 is formed between the outmost free ends of the fan blades 14 and the side wall 23 of the fan frame 20.

Referring to FIG. 4, during operation, the high-pressure airflow generated by the fan blades 14 accumulates in the air flow channel 30 and flows towards the air outlet 25 along the side wall 23 of the fan frame 20. As the impeller 10 rotates, the high-pressure airflow generated by the fan blades 14 will impinge on the side wall 23 of the fan frame 20, as indicated by arrows in FIG. 4. After being impinged on the side wall 23, a portion of the high-pressure airflow will rebound back towards the fan blades 14. Air turbulence will be generated between the high-pressure airflow generated by the fan blades 14 and that portion of airflow being rebounded back, thereby causing large air noise and energy loss. Due to the presence of the ribs 146 formed adjacent to the outmost free ends of the fan blades 14, the refluxed airflow is blocked by the ribs 146 at the outmost free ends of the fan blades 14 to flow back into the fan blades 14 of the centrifugal fan. Furthermore, the refluxed airflow is also blocked by the sidewall 162 of the blade ring 16 to flow back, via the axial clearance between the connecting wall 160 of the blade ring 16 and the top cover 21, towards the first air inlet 24 a of the centrifugal fan due to the presence of the blade ring 16. As a result, the ribs 146 and the blade ring 16 cooperatively reduce air turbulence caused by the refluxed airflow so that noise generated by the air turbulence is greatly reduced.

In order to effectively block the refluxed airflow, the angle θ formed between the rib 146 and the outmost free end of the second blade portion 144 of the fan blade 14 is not limited to 65 degrees. The angle θ can be varied in a range of about 65 degrees to about 90 degrees.

FIG. 5 and FIG. 6 show an impeller 10 a for a centrifugal fan in accordance with a second embodiment of the present invention. Except for the shape of the blade ring 16 a, other parts of the impeller 10 a in accordance with this second embodiment have substantially the same configurations as the impeller 10 of the first embodiment. More specifically, the blade ring 16 a includes a top planar connecting wall 160 a, a cylindrical sidewall 1622 extending perpendicularly and downwardly from an outer periphery of the connecting wall 160 a and a flange 1624 extending radially and outwardly from a bottom of the sidewall 1622. In assembly, the blade ring 16 a is received in the first air inlet 24 a of the centrifugal fan. The connecting wall 160 a of the blade ring 16 a covers on and overlaps with the top faces of the second blade portions 144 of the fan blades 14. A top surface of the connecting wall 160 a of the blade ring 16 a is coplanar with the top surface of the top cover 21 of the centrifugal fan. The outer periphery of the connecting wall 160 a is substantially aligned with an outmost longitudinal edge of each of the fan blades 14. The sidewall 1622 of the blade ring 16 a surrounds a top edge portion of the outmost longitudinal edge 144 b of each of the fan blades 14. The flange 1624 of the blade ring 16 a is located directly under and overlaps with the top cover 21 of the centrifugal fan. In this second embodiment, the high-pressure airflow in the air flow channel 30 can be blocked by the sidewall 1622 to flow back towards the first air inlet 24 a of the centrifugal fan due to the presence of the blade ring 16 a, thereby reducing air turbulence caused by refluxed airflow in the centrifugal fan so that noise level is reduced. Additionally, since the connecting wall 160 a of the blade ring 16 a and the top cover 21 are coplanar with each other, a longitudinal height of the second blade portion 144 of each of the fan blades 14 under the connecting wall 160 a can be increased about 1 mm, which makes air pressure and amount of airflow increase during operation of the centrifugal fan.

It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. 

1. A fan impeller comprising: a hub; and a plurality of fan blades extending radially and outwardly from an outer periphery of the hub, each of the fan blades having a leeward lateral surface and an opposite windward lateral surface, at least one of the fan blades having a rib protruding longitudinally and outwardly from the leeward lateral surface of the fan blade, the rib being located adjacent to an outmost free end of the fan blade and adapted for blocking an airflow generated by the fan impeller to flow back towards the fan blades of the fan impeller.
 2. The fan impeller as described in claim 1, further comprising a blade ring having an annular connecting wall covered on top surfaces of the fan blades and a vertical sidewall connected with the connecting wall.
 3. The fan impeller as described in claim 2, wherein the sidewall extends upwardly from an inner periphery of the connecting wall.
 4. The fan impeller as described in claim 2, wherein the sidewall extends downwardly from an outer periphery of the connecting wall and the blade ring further includes a flange extending radially and outwardly from a bottom of the sidewall.
 5. The fan impeller as described in claim 4, wherein the outer periphery of the connecting wall is substantially aligned with an outmost longitudinal edge of each of the fan blades and the sidewall surrounds a top edge portion of the outmost longitudinal edge of each of the fan blades.
 6. The fan impeller as described in claim 1, wherein the rib is formed at each of the fan blades, an angle formed between the rib and the outmost free end of the fan blade being varied in a range of about 65 degrees to about 90 degrees.
 7. The fan impeller as described in claim 1, wherein each of the fan blades comprises a first blade portion connected with the hub and a second blade portion bent slantwise and smoothly from a distal end of the first blade portion, the rib located at the second blade portion of the fan blade.
 8. A centrifugal fan comprising: a fan frame comprising a bottom base, an opposite top cover and a side wall interconnecting the base with the cover; and a fan impeller rotatably received in the fan frame, the fan impeller comprising a hub and a plurality of fan blades extending radially and outwardly from an outer periphery of the hub, each of the fan blades having a leeward lateral surface and an opposite windward lateral surface, at least one of the fan blades having a rib protruding longitudinally and outwardly from the leeward lateral surface of the fan blade, the rib being located adjacent to an outmost free end of the fan blade and adapted for blocking airflow rebounded by the side wall of the fan frame to flow back towards the fan blades of the fan impeller.
 9. The centrifugal fan as described in claim 8, wherein the fan impeller further comprises a blade ring having an annular connecting wall covered on top surfaces of the fan blades and a vertical sidewall connected with the connecting wall.
 10. The centrifugal fan as described in claim 9, wherein the connecting wall of the blade ring is located just under the top cover of the fan frame, and the sidewall extends upwardly from an inner periphery of the connecting wall to be flush with a top surface of the top cover.
 11. The centrifugal fan as described in claim 9, wherein the sidewall of the blade ring extends downwardly from an outer periphery of the connecting wall and the blade ring further includes a flange extending radially and outwardly from a bottom of the sidewall.
 12. The centrifugal fan as described in claim 11, wherein the outer periphery of the connecting wall is substantially aligned with an outmost longitudinal edge of each of the fan blades and the sidewall of the blade ring surrounds a top edge portion of the outmost longitudinal edge of each of the fan blades.
 13. The centrifugal fan as described in claim 11, wherein the connecting wall of the blade ring is coplanar with the top cover of the fan frame, and the flange of the blade ring extends into the fan frame and is located just under the top cover of the fan frame.
 14. The centrifugal fan as described in claim 8, wherein the rib is formed at each of the fan blades, an angle formed between the rib and the outmost free end of the fan blade being varied in a range of about 65 degrees to about 90 degrees.
 15. The centrifugal fan as described in claim 8, wherein each of the fan blades comprises a first blade portion connected with the hub and a second blade portion bent slantwise and smoothly from a distal end of the first blade portion, the rib located at the second blade portion of the fan blade. 